CIRCULATING INHIBINS AND ACTIVIN-A DURING GNRH-ANALOG DOWN-REGULATIONAND OVARIAN HYPERSTIMULATION WITH RECOMBINANT FSH FOR IN-VITRO FERTILIZATION-EMBRYO TRANSFER

OBJECTIVE We have investigated serial changes in plasma concentrations of inhibin A, inhibin B, pro alpha C and activin A in women undergoin g stimulation with recombinant FSH in 'long-protocol' down-regulated c ycles of IVF treatment. DESIGN Blood samples were collected during the entire IVF treatment cycle at points coinciding with the early follic ular phase of the cycle preceding treatment, pituitary down-regulation , stimulation with recombinant FSH, ovulatory triggering, and the lute al phase of the cycle. In patients who achieved conception, blood samp les were also taken during the first 2 weeks of pregnancy. All samples were analysed for inhibin A, inhibin B, pro alpha C, activin A and oe stradiol. PATIENTS Fifteen women with normal ovarian function undergoi ng IVF treatment with tubal factor, mild endometriosis or idiopathic i nfertility. RESULTS During pituitary desensitization, both inhibin A a nd inhibin B were significantly (P < 0.001, P = 0.002, respectively) r educed whereas levels of pro alpha C and activin A were largely unalte red. Levels of both inhibins rose markedly (P < 0.01) during FSH stimu lation and a further rise in inhibin A was detected on the day after o vulatory trigger. Levels of both inhibin A and inhibin a then fell dur ing and after oocyte pickup and continued to fall during the luteal ph ase. Activin A levels rose less markedly during gonadotrophin stimulat ion. Statistical analysis showed a high degree of correlation between the number of follicles (> 10 mm) and serum inhibin A (r = 0.65, P < 0 .01) and pro alpha C (r = 0.65, P < 0.01) concentrations during the la te follicular phase. CONCLUSIONS These results indicate that ovarian p roduction of dimeric inhibin A and B are gonadotrophin dependent, wher eas activin A may have a significant gonadotrophin independent or extr a-gonadal source. Inhibin A and pro alpha C may be useful markers for monitoring the effects of gonadotrophin stimulation.